Evolution of radio access methods and radio networks in cellular mobile communication (hereinafter called a “Long Term Evolution (LTE)” or “Evolved Universal Terrestrial Radio Access (EUTRA)”) is studied in the 3rd Generation Partnership Project (3GPP). The LTE employs, as a communication method for radio communication from a base station device to a mobile station device (i.e., for a downlink), Orthogonal Frequency Division Multiplexing (OFDM) that is multi-carrier transmission. The LTE further employs, as a communication method for radio communication from a mobile station device to a base station device (i.e., for an uplink), SC-FDMA (Single-Carrier Frequency Division Multiple Access) that is single-carrier transmission. In the LTE, the base station device is called an enhanced NodeB (eNodeB), and the mobile station device is called User Equipment (UE).
In the LTE, the base station device employs Downlink Control Information (DCI) for instructing the mobile station device to perform initial transmission or retransmission for PUSCH (Physical Uplink Shared Channel) that is a channel for transmitting uplink data (also called “uplink shared channel (UL-SCH))”. The Downlink Control Information is transmitted with PDCCH (Physical Downlink Control Channel).
In the LTE, MU-MIMO (Multi User-Multiple Input Multiple Output) is introduced to improve a capacity. The MU-MIMO implies a technique enabling each of plural mobile station devices to transmit one or plural data series at the same time and at the same frequency using PUSCH, and enabling a base station device to separate, per mobile station device, the one or plural data series transmitted from each of the mobile station devices upon receiving them.
However, because the plural data series from the plural mobile station devices are spatially multiplexed at the same frequency, interference with an adjacent cell increases. FIG. 7 illustrates interference signals interfering with an adjacent cell in related art. In a cell A illustrated in FIG. 7, a mobile station device 1A and a mobile station device 1B transmit signals to a base station device 3A, and the signal from the mobile station device 1A and the signal from the mobile station device 1B are spatially multiplexed. In a cell B illustrated in FIG. 7, a mobile station device 1C and a mobile station device 1D transmit signals to a base station device 3B. In such a situation, both the signal from the mobile station device 1A and the signal from the mobile station device 1B interfere with the cell B, while both the signal from the mobile station device 1C and the signal from the mobile station device 1D interfere with the cell A.
Non Patent Literature (NPL) 1 describes a technique of reducing power of a signal transmitted from each mobile station device depending on the number of mobile station devices which are scheduled at the same frequency, aiming to suppress the interference with the adjacent cell. With the technique of NPL 1, the mobile station device calculates transmission power based on a formula (3) in NPL 1.